Use of Uncoated CaCO₃ (Malaysia, High-Whiteness) in PVC Pipe
Overview:
Malaysian uncoated calcium carbonate with higher whiteness/brightness is ideal for white and pastel PVC pipes as well as coloured pipes. The cleaner undertone reduces yellow/cream cast and improves appearance without heavy TiO₂ reliance.
Key advantages
Whiter base & cleaner tone → brighter whites/pastels; tighter ΔE across batches.
TiO₂ optimization → potential 2–10% reduction in TiO₂ usage (verify by drawdowns).
Smooth surface & gloss → fine particle distribution lowers surface defects and die lines.
Rigidity & dimensional stability → maintains ring stiffness while controlling shrinkage/warpage.
Processing aid → consistent extrusion, stable melt, less plate-out with correct lube balance.
Recommended use (rigid PVC pipe)
Loading: 8–20 phr (≈6–15% by weight), adjust for stiffness/impact targets.
White & pastel pipes: Prefer Malaysian CaCO₃ as the primary filler; fine-tune TiO₂ to target L* and b*.
Coloured pipes: Use freely; the high whiteness helps pigments achieve brighter, cleaner shades.
QC & specs to watch
Whiteness/Brightness (L, b)** — set tighter internal limits than standard grades.
CaCO₃ ≥ 96–98%, Moisture ≤ 0.3%, Residue on 325 mesh: minimal, pH ~9–9.5.
Check dispersion (thin-slice microscopy) and plate-out; balance external lubricants (PE/ester wax).
Blending strategy
For cost control, blend Malaysian (high-whiteness) with a standard grade (e.g., Oman) in coloured pipes.
For white pipes, keep Malaysian grade ≥70% of total CaCO₃ to preserve brightness and reduce TiO₂.